RetroFlag GPi Case - A 'GBZero' that isn't janky

Modding an OG gameboy to house a Raspberry Pi Zero (or CM3) has been a thing for a while. Unfortunately it's always been a pricey proposition, requires more than a little electronic and physical modification, and the quality of the finished product can vary wildly depending on your skill level.

Now Retroflag (a company known for making some of the nicer mini-console-inspired RPi cases) has taken all of the drilling, cutting, and soldering out of the equation. Their case comes completely assembled. All you have to do is install your Raspberry Pi Zero or Zero-W in the cart (it has a pogopin connector), stick some AA batteries in it, and away you go. The design includes a safe shutdown switch, a microUSB port for firmware updates, and the cleverest L/R buttons I've seen on a GBZero.

The GPi case is a bit smaller than an OG gameboy, but it keeps the original proportions and styling cues. It's a bit bigger than the bitboy, but more true to the original design and layout.

It's not for sale quite yet, but review units have gone out to a few youtubers. I've included ETAPrime's review and teardown below. It'll be $70 whenever it becomes available, hopefully soon.

I'd have thought a CM3 would be enough to run 60fps SNES games and maybe even PS1 (since it includes NEON instructions unlike the Pi-Zero line). They're a little underclocked compared to a full fat Pi3, but still 64-bit capable and got all of the other gubbins, so a long way from an old-fashioned Pi Zero.

The cool thing is that they could just sell a replacement "cartridge" with uSD and SODIMM sockets instead of the pogopins, and it should work just fine. I can probably sketch one up in eagle in about 15 min and get the board made for a few bucks.

Like I said though, a CM3 PCB should be trivially-simple. I don't know how long it would manage to run on AA batteries, but it would definitely work.

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That's a good question. The CM3 is rated at 3.5W I think, while the Pi Zero non-W is a 1.75W part, so at minimum with everything running at max, a CM3 based unit should last about half as long on a set of AAs.

Great engineering and ideas were put in this it seems, those L+R buttons alone! I really love stuff like this, is this an injection molded case? They are pretty confident then to sell alot and I'm sure it will pay off.

It's hard to sell a product like this using 3d printed parts, I assume. You'd need to take time to produce the parts with 3d printing, and drip feed units into the market. To make the best of a relatively short but high intensity sales window, you need to be able to produce parts quickly, so that you can stockpile them for launch and get them sent out quickly. If the product line proves to have a longer lifespan, then you've still got the moulds also, making it cheaper and quicker to keep making cases. Of course, if you can't sell a couple thousand units at launch, then you might need to rely on 3d printing, but that doesn't tend to result in happy consumers having to wait when youtube is full of released parts.

That's a good question. The CM3 is rated at 3.5W I think, while the Pi Zero non-W is a 1.75W part, so at minimum with everything running at max, a CM3 based unit should last about half as long on a set of AAs.

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If AAs can even supply enough current to run the CM3 at all. I think a CM3 cart would have to go hand in hand with a lipo upgrade.

The three AAs are wired in series, so they're supplying anywhere from 3-5V depending on their charge level. Clearly the power circuit can handle that range.

Three 900mAH 14500 lipos in parallel would supply 3.2-4.2V, so within the valid range. It would only take some minor modification to convert the case to this configuration, and only slightly more work to add a microUSB lipo charging board and safety cutout. A couple LEDs and diodes could provide battery level indication. At that point, you basically have a "perfect" CM3 gameboy.

Yes, if three alkaline AAs are only producing 1V each, they're pretty much on their way out for most uses. I generally toss them when the hit about 1.2V no load.

According to this site you're looking at terminal dropoff at about 2h15m at 1A/around 3.5W.

The Pi Zero by comparison is rated at 1.75W max load which is about 400mA per cell. According to the charts there that actually only gives you up to about 15 minutes actual extra play time, which surprises me slightly. Seems like alkaline cells are basically constant discharge, so if you drop the current by half you actually only get slightly more than half of the total capacity by the time the cell is dead.

So it seems that if you're talking alkalines then you may as well shank the battery for all it's got. I couldn't identify any lithium batteries on there, although they're supposed to be better.

Ugh. It appears the CM3 is actually slightly wider than the zero, and the zero looks like it's already a pretty tight fit. The zero is 65mm, and the slimmest SODIMM connector I can find is just under 71mm. I don't think there's an extra 6mm in there without trimming plastic.

Ugh. It appears the CM3 is actually slightly wider than the zero, and the zero looks like it's already a pretty tight fit. The zero is 65mm, and the slimmest SODIMM connector I can find is just under 71mm. I don't think there's an extra 6mm in there without trimming plastic.

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It gets worse - apparently the CM3 needs 3.3V and 1.8V supplies, and doesn't do analog audio out without a good deal of futzing with the kernel config. I still don't think any of these issues are insurmountable, but it's looking like a bigger project than just slapping a 200 pin connector on a board and routing it to some contact pads. I'll take some measurements when I get mine and see if it's worth trying to suss out.

Apparently the banana pi people make an allwinner H2-powered board that is a drop-in replacement for the RPi zero. It's significantly more powerful, and should allow the GPi case to handle SNES and GBA games at full speed, as well as make a lot more PS1 games playable.

Power usage is (predictably) higher, so a lipo conversion will be pretty much mandatory. But otherwise, this looks like a great upgrade.

The H2 is a cortex A7 1GHz x4 part. I dunno if emulators efficiently use multiple cores yet, sometimes when you need cycle exact implementations splitting execution units across different cores can make coding a lot more complex, so assuming they don't you could hopefully turn three of those cores as low as they can go. I single A7 running at 1GHz should take less grunt than an old ARM11 chip at 1GHz (as found in the Pi Zero), I'd have thought.

I think the GameBoy shell is great for 2 or 4 button games, horrible for everything else. I don't know why everyone copies it over the GBA, which can have 6 buttons and if they go for a 6 face buttons layout like a Nomad/genesis/mega drive it can have 8 buttons, the same as a PS1 controller. If retro flag makes it they might have the handy feature of select+R+L combo to switch the shoulder buttons with two of the face buttons like their 6 buttons MD pad does now.

I know the original GB is Nostalgic and everyone and their dog had one back in the day and it brings back fuzzy feelings in the hands but when you try to play anything that requires more than 4 buttons it just isn't an ideal layout.

I'll wait for RetroFlag to make a GBA shell. And hopefully like they did with this shell they'll throw in extra face buttons for good measure. The pi zero in the cart was genius though, hopefully they'll keep that to make it easy to set up.